INTRAPELVIC INJECTION OF MENSTRUAL ENDOMETRIUM CAUSES ENDOMETRIOSIS IN BABOONS (PAPIO-CYNOCEPHALUS AND PAPIO-ANUBIS)

OBJECTIVE: The Sampson hypothesis of retrograde menstruation as a caus e of endometriosis was tested by determining the effect of intrapelvic injection of menstrual versus luteal endometrium on the incidence, pe ritoneal involvement, and stage of endometriosis. STUDY DESIGN: Sevent een baboons were injected retroperitoneally with luteal (n = 6) or men strual (n = 7) endometrium and intraperitoneally with menstrual endome trium (n = 4). Laparoscopies were performed after 2 months in all anim als and after 5 and 12 months in six and five primates injected with l uteal and menstrual endometrium, respectively. RESULTS: The peritoneal endometriosis surface area, number of implants, and incidence of typi cal and red subtle lesions were significantly higher after retroperito neal injection of menstrual than of luteal endometrium. By use of mens trual endometrium intraperitoneal seeding was more successful in causi ng endometriosis than was retroperitoneal injection. No significant ch anges in number or surface area of endometriotic lesions induced with retroperitoneal injection of luteal endometrium after 5 months were ob served in the six baboons. At repeat laparoscopy 12 months after intra pelvic injection of menstrual endometrium progression was recorded in three of four regularly cycling animals, whereas regression was eviden t in one baboon that had become amenorrheic after induction. CONCLUSIO N: Intrapelvic injection of menstrual endometrium can cause peritoneal endometriosis and offers experimental evidence supporting the Sampson hypothesis.